18019_Standard_Uniform_Indoor_Air_Results

3.4 Indoor Air Sample Results
The results of field measurements taken during the indoor air sampling are summarized in Table2. During the sampling event, outside temperatures were in the range of 85 to 101oF. In
indoorair temperatures ranged from 72 to 74oF in the conditioned spaces to 80 to 88oF in thewarehouse. The results of the differential pressure measurements indicate that differentialpressure
was primarily neutral to slightly negative (pressure was higher inside than outside)during most of the sampling event.
The results of analysis of the indoor air samples are summarized in Table 5. The results indicatethat no compounds were detected in the samples above the conservative DWM Non-ResidentialIndoor
Air Screening Levels (IASLs). PCE was detected in the highest concentrations rangingfrom 5 μg/m3 to 26 μg/m3 versus the DMW Non-Residential IASL of 35 μg/m3. In addition, alow level
of PCE (0.38 μg/m3) was detected in the background outdoor sample (BAS-1). Lowconcentrations of TCE ranging from 0.12J μg/m3 to 0.62 μg/m3 were detected in the indoor airsamples which
are below the DWM Non-Residential IASL of 1.75 μg/m3. Consistent with thesub-slab soil vapor data, the highest PCE and TCE concentrations were detected in sample IAS-3in the southeastern
portion of the warehouse.
As noted above, the compound concentrations detected in the indoor air samples were comparedto the Non-Residential IASLs. These screening levels are very conservative and based upon
aLifetime Incremental Cancer Risk (LICR) of 1 x 10-6 for potential carcinogenic effects and/or aHazard Index (HI) of 0.2 for potential noncarcinogenic effects. Vapor intrusion mitigation
foroccupied Industrial/Commercial structures is not typically considered unless the LICR exceeds 1x 10-4 for potential carcinogenic effects and a HI of 1 for potential non-carcinogenic
effects.
To further evaluate the risks posed by the detected compounds, H&H calculated cumulativepotential carcinogenic and non-carcinogenic risks for the five indoor air samples collected fromthe
site building. The calculations and equations are summarized in Table 6. The highestcalculated LICR and HI came from the concentrations detected in IAS-3. Both the LICR (7.6 x10-7)
and HI (0.22) are well below the acceptable risk thresholds of LICR of 1 x 10-4 HI of 1.